In Local Area Networks (LAN) of a ring architecture there is a major problem of how to handle network failures that open the ring and stop communications. In a commercially successful ring network of the present assignee, the loop communication path of the ring network is of a multiple petal configuration, with the path to and from each node extending through a central "petal isolator" at which each node can be bypassed manually in the event of a failure. It is conceived that significant improvements are possible in automating such a petal isolator system, particularly in avoiding any need for the transmission and reception of special test signals at the central petal isolator location.